A research group led by Professor Seiji Kadowaki and Associate Professor Kazuhiro Tsukada of Nagoya University Museum, Graduate School of Environmental Studies at Nagoya University; Researcher Ayami Watanabe of Nagoya University Museum; and Graduate Student Eiki Suga of the Graduate School of Environmental Studies at Nagoya University, in collaboration with Meiji University, the National Institute of Advanced Industrial Science and Technology, Kiso Regional Union, and the Jordan Department of Antiquities and Jordan Tourism Board, has announced that they have quantitatively clarified the cultural evolution at the time Homo sapiens spread throughout Eurasia (approximately 50,000 to 40,000 years ago). Examination of the cutting-edge productivity (production efficiency) of stone tools revealed that approximately 45,000 years ago, stone tools were thick and heavy, whereas their miniaturization about 40,000 years ago improved their productivity. It also revealed that at the same time, the population of H. sapiens increased in various parts of Eurasia, and archaic humans became extinct. The results were published in the international academic journal Nature Communications on February 7, 2024.
H. sapiens are the only existing human beings, but Neanderthals, Denisovans, and Homo floresiensis also existed 50,000 years ago. H. sapiens spread to and multiplied in Eurasia, leading to the extinction of the other species in various regions between 50,000 and 40,000 years ago. H. sapiens and Neanderthals co-existed for more than 100,000 years and were close enough to interbreed, but their fates diverged sharply. However, little is known about how and when the diverse cultures and technological innovations of H. sapiens arose.
The research group focused on stone tool technology to examine this issue. They conducted five excavations in Jordan in the Middle East from 2016 to 2022 and discovered eight lithic assemblages from five ruins. These assemblages include stone tools from the Initial Upper Paleolithic period, which corresponds to the time when H. sapiens began to spread throughout Eurasia (about 45,000 years ago).
To quantify when and how innovation in stone tool technology occurred using consistent indicators, they investigated diachronic changes in cutting-edge productivity. The efficiency of stone tool production was quantified in terms of the length of the cutting edge that can be obtained per mass of stone. The lengths of cutting edges of stone tools were measured based on their digital photographs using image-editing software, and only sharp blades were extracted. The analysis revealed that the stone tools used by H. sapiens in the Initial Upper Paleolithic period (about 45,000 years ago), when they began to spread throughout Eurasia, were thick and heavy, and cutting-edge productivity was low. It also revealed that cutting-edge productivity at this time was lower or similar to that in the prior Late Middle Paleolithic period. The productivity increased in the subsequent Early Upper Paleolithic period (approximately 40,000 to 30,000 years ago). The small stone tool, called "bladelet," technology was also shown to have been developed in this period. The results showed that the increase in cutting-edge productivity was achieved through the miniaturization of stone tools.
This period corresponds to the time when the population of H. sapiens increased in various parts of Eurasia and archaic humans became extinct. In terms of cutting-edge productivity, it turns out that innovation of stone tool technology by H. sapiens occurred not in the Initial Upper Paleolithic period, when they began to spread throughout Eurasia, but in the Early Upper Paleolithic period, when the H. sapiens population increased in various parts of Eurasia.
Kadowaki opined, "Increased cutting-edge production efficiency means that the consumption of stone materials becomes more economical. The advantage of this is that the labor to bring the stone materials can be used for other tasks such as acquiring food. We revealed that modern humans have increased cutting-edge productivity by miniaturizing stone tools, but small stone tools also have disadvantages, such as being difficult to hold in the hand. In the future, we would like to clarify how they made full use of the stone tools."
Journal Information
Publication: Nature Communications
Title: Delayed increase in stone tool cutting-edge productivity at the Middle-Upper Paleolithic transition in southern Jordan
DOI: 10.1038/s41467-024-44798-y
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.